In centrally controlled communications networks, e.g., in a centrally controlled wireless cellular network according to the HYPERLAN type 2 ETSI Project, a central unit ZE is provided to which a plurality of terminals can be connected (see FIG. 1). This wireless network functions in a connection-oriented manner, i.e., at least one connection must be established before data can be exchanged with other subscribers or their terminals, which are connected to the network or to master station ZE. On the basis of subscriber demands, the master station assigns the terminals the data rate they need on the shared medium. It is possible for one terminal of one subscriber to have more than one active virtual connection at the same time, as is the case with ATM. In an implementation form of this network, the resource requests by the terminals as well as the resource allocations (resource grants) by master station ZE are carried out per connection, i.e., the terminal transmits the amount of data packets that need to be transmitted for each of its connections. Providing data rates during which data can be transmitted on the medium is considered a resource here. Accordingly, master station ZE transmits a resource allocation for each connection of terminal T. In the case of the resource allocation per connection, the assignment of a transmitted data packet to a connection is explicitly provided by the allocation of master station ZE. Thus, this information is already present in master station ZE and does not need to be additionally transmitted by the terminal.
In the aforementioned wireless network, two different data packet sizes are provided for the data to be transmitted. In this context, short packets (approximately 6 bytes; short data container: KD) are used for transmitting control information, i.e., information that is not useful data but is used to control and manage the network, e.g., to establish connections, to associate terminals, to carry out handovers, or to re-request incorrectly received data packets, for example. Long data containers LD have a length of about 54 bytes and are normally used for transmitting useful data. In addition to pure useful data, further information is included that is closely related to the useful data, e.g. a sequence number or a checksum for error detection.
A transmission in the downlink direction (master station toward the subscriber) as well as in the uplink direction (terminal toward the master station) includes a plurality of control data packets KD at the beginning and a subsequent plurality of useful data packets LD according to FIG. 2. The exact number of control data packets KD and useful data packets LD is determined by master station ZE in the resource allocation.
A method for transmitting in a communications system in a frame-oriented form between a master station and a plurality of subscribers is described in Raychaudhuri D. et al., “WATM net: A Prototype Wireless ATM System for Multimedia Personal Communication,” IEFE International Conference on Communications (ICC), U.S. New York, IEFE, Jun. 23, 1996 (1996-06-23), pages 469–477. In this instance, useful data packets and control data packets are exchanged. An identifier is stored in the header of a data cell, for transmitting in a connection-oriented manner.